Optimized Synthesis and Fpga Implementation of a Fir Filter for Multiple Position Equalization of a Recording Studio/concert Hall

This paper presents an improved approach to the synthesis and implementation of digital filters employed for multiple position equalization of a room transfer function. First, we propose a more effective way of deriving the desired frequency response of the equalizer than the Levinson-Durbin algorithm employed by well-known method used here as a reference to compare against. Second, the equalizer is implemented by a FIR filter synthesized by using an optimized procedure, based on a genetic algorithm that curtails the differences between the wanted and synthesized frequency responses while minimizing the filter length. These two features help us reduce significantly the hardware requirements for implementing the resulting equalizer. The effectiveness of the proposed method is demonstrated on a real-life example: the implementation of a FIR filter able to equalize the room transfer function of a recording studio used also as a concert hall. The optimized synthesis procedure yielded a FIR equalizer whose number of taps was reduced by an order of magnitude compared to the results reported by the reference method. The circuit implementation of the equalizer required only a small fraction of the resources provided by a mid-range FPGA development board. Objective and subjective measurements were carried out with and without the equalizer being inserted in the acoustic chain; they showed clearly that the proposed equalizer improved significantly the audition.